1. Field of the Invention
The invention relates to optical devices and more particularly to protecting and/or stabilizing color filter material overlying optical devices.
2. Description of Related Art
Digital imaging systems, such as for example digital cameras, utilize integrated circuit devices or chips as image capturing devices. An imaging system, such as a camera, uses light to capture an image on a semiconductor-based chip. The chip replaces film in traditional film-based systems. In a digital camera, an image sensor is configured, in its simplest form, to capture a monochrome or color image by way of field effect transistors (FETs), such as complementary metal oxide semiconductor (CMOS) devices or charge coupled devices (CCDs).
In one example, the image sensor is a semiconductor chip made up of a number of photosensing structures, such as photodiodes, each photodiode capable of absorbing light. In color applications, each photodiode generally absorbs light through a color filter that represents a particular wavelength of light in the visible spectrum corresponding to the image sensed.
The image sensor contains a plurality of pixels, such as for example 480 rows by 640 columns of pixels. In general, each pixel contains a photosensing structure, such as a photodiode, and other pixel circuitry. The photosensing structure defines a photosensing region or area of the pixel that responds to light while the pixel circuitry, generally speaking, drives a light signal from the photosensing region or area to other process circuitry.
As noted above, one method of converting a monochromatic digital imager into a color imager involves absorbing light through a color filter. The color performance of any color filter concerns the ability of the filter to select color corresponding to the desired wavelength of the visible spectrum of the color filter array (CFA) material. A common color filter material is spin coated, dyed- or pigmented-photoresist CFA material. The commonly used CFA materials generally experience aging problems, notably the deterioration of color performance. The deterioration is accelerated by exposure of the CFA material to elevated temperature or moisture. The transmissivity of CFA material changes due to exposure of the material to these and other deleterious environmental effects. This degradation is most evident with respect to Blue CFA material. One experiment found the transmissivity of Blue CFA material was reduced about 40% after ten hours in a 230xc2x0 C. exposure. This effect will be magnified in the presence of humidity. Other CFA materials (e.g., Red, Green, etc.) also see significant reductions.
Thus, what is needed is a way to protect CFA material from aging and environmental effects. The protection should not effect the performance of the CFA material or the image sensing or displaying properties of the device.
An optical device that includes a filter material overlying an area over a photosensitive portion of the device. The optical device also includes a silylation layer overlying the filter material.
Additional features and benefits of the invention will become apparent from the detailed description, figures, and claims set forth below.